Genesis of meta-gabbroic crustal xenoliths found in Neogene/Quaternary alkali olivine basalt, northeastern Iran

Abstract

Rounded to angular granoblastic textured mafic xenoliths, ranging from ∼1 to 6 cm in dimension, occur together with mantle peridotite xenoliths in a small Neogene/Quaternary alkali basalt cone in northeastern Iran. These crustal xenoliths consist of plagioclase feldspar, clinopyroxene, orthopyroxene and minor olivine, spinel, titanomagnetite and apatite. Their bulk compositions are similar to tholeiitic basalts and they are interpreted as meta-gabbroic rocks derived from mid- to lower crustal depths of 18 to 30 km. Rb–Sr dating suggests an age of c. 457 ± 95 Ma for these crustal xenoliths, and their geochemistry shows some similarities to Ordovician gabbros that crop out ∼20 km to the west. The data suggest that the gabbroic proto-lithologies of the xenoliths formed by intrusion of mafic magmas into the mid- to lower crust, possibly during extension and magmatism related to the opening of the Hercynian Palaeotethys ocean that separated central and eastern Iran from the Eurasian plate during the Late Palaeozoic.

Time Series Characteristics of Terrain Data

“…Traditional Chinese geography believes that terrain is dynamic. Different from the modern plate movement theory's focus on the formation of the crust [2][3][4] [5] [6],the ancient Chinese paid more attention to the impact of dynamic terrain on the real world in everyday life [7]. However, the West takes a different approach [8].…”